1. Field of the Invention
This invention relates to the field of valves, and in particular to a rotary disc valve specifically designed for use in an injection mold cooling system.
2. Description of the Related Art
In the injection molding process, hot material is injected into a cavity within a mold for formation into useful articles. The mold is then cooled by circulating cooling water through a plurality of cooling passages which pass through the mold. The cooling water is provided from a cooling water source through an inlet line to a supply manifold which is, in turn, connected to the mold by a plurality of mold supply lines. The cooling water flows from the mold through a plurality of mold return lines to a return manifold, and then into a return line where it is channeled back to the source.
When it is time to change molds, the cooling water supply must be shut off and then the mold supply and return lines must be disconnected from the mold. If the cooling water is not drained from the mold and the supply and return lines before the lines are disconnected, cooling water will be spilled on the floor surrounding the injection molding machine. Cooling water on the floor can present a safety hazard to personnel working around the molding machine, and therefore time and resources must be expended to clean it up. Each individual supply and return line can be drained as it is disconnected, however this is a time consuming process which still often results in spills which must be cleaned up.
What is needed is an efficient way to purge all of the cooling water from the mold cooling system before the supply and return lines are disconnected. In order to accomplish this task, a valve must be provided which can selectively supply cooling water and purge air to the mold. Another convenient feature would be if the valve incorporated a vent for releasing the purge air to the atmosphere after the mold is purged of cooling water.
Multi-way valves are well known in the art, however none of these valves is ideally suited for use in an injection mold cooling system as described. Many are unnecessarily complex and expensive to manufacture. A rotary disc valve is disclosed by U.S. Pat. No. 3,405,734 to G. H. Smit, et al., entitled Self-Draining Valve. This valve is designed for use as a distribution valve in cold weather outdoor applications where a valve must be self-draining to prevent it from freezing and breaking.
The valve includes a disc which is rotatably mounted between inlet and outlet side plates. The outlet side plate includes multiple outlet passages and a drain passage which are spaced radially outwardly from the axis of rotation of the disc, which is defined by a bolt passing through the center of the disc and both side plates. The inlet side plate includes a single inlet line which is spaced radially outwardly from the axis of rotation of the disc and connects to an annular trough which is machined into the inner surface of the inlet side plate. The disc includes a single bore which passes completely through the disc and is spaced radially outwardly from the axis of rotation of the disc so that it stays in communication with the annular trough of the inlet side plate as the disc is rotated. By rotating the disc, the disc bore can be brought into communication with one of the outlet passages, allowing fluid to flow through the valve from the inlet passage to that outlet passage. The disc further includes a generally annular groove formed in the side adjacent the outlet side plate of the valve. This groove is designed to communicate the outlet passages to the drain passage when the valve is in the off position, allowing the outlet lines to drain.
The valve disclosed by Smit, et al. is not specially designed for use as a purge valve for a injection mold cooling system and would be unnecessarily complex for this application as its self-draining features are not required in a heated indoor molding facility. What is needed is a simple, compact, and economical rotary disc valve which is suitable for use as a purge valve in an injection mold cooling system.
The present invention comprises a rotary disc valve which may be configured as a three-way purge valve for use in an injection mold cooling system. The valve generally includes a housing having an inlet side and an outlet side, and a disc mounted within the housing between the inlet side and the outlet side thereof, the disc being rotatable about its central axis. The disc has an inlet face which is adjacent the inlet side of the housing and an outlet face which is adjacent the outlet side of the housing. The disc is provided with a handle which extends radially outwardly from the disc outer circumferential surface which is used for manually rotating the disc relative to the housing.
The inlet side of the housing includes a plurality of inlet side passages which are spaced radially outwardly from the axis of rotation of the disc and extend through the inlet side of the housing such that they communicate with the inlet face of the disc. The outlet side of the housing includes a single outlet passage which is generally aligned with the axis of rotation of the disc and extends through the outlet side of the housing such that it communicates with the outlet face of the disc.
The disc includes an outlet bore which is generally aligned with the axis of rotation of the disc and extends from the outlet face of the disc partially through the disc. One or more inlet bores spaced radially outwardly from the axis of rotation of the disc extend from the inlet face of the disc partially through the disc and communicate with the outlet bore.
The inlet bore or bores are located such that a bore may be selectively brought into communication with a single one of the inlet side passages by rotating the disc until the bore is aligned with the desired passage. Since the outlet bore and outlet passage are aligned along the center of rotation of the disc, the outlet bore stays in constant communication with the outlet passage in the outlet side of the housing as the disc is rotated. Therefore, by rotating the disc until an inlet passage is aligned with a respective disc inlet bore, that inlet passage is brought into communication with the outlet passage, making it possible for a fluid to flow through the valve between the inlet and outlet sides.
When configured for use as part of an injection mold cooling system the inlet passages are designated as a cooling water inlet passage and a purge air inlet passage. The inlet side of the housing may also be equipped with an air vent passage for releasing purge air from the cooling system after the cooling water is purged out.
The principal objects and advantages of the present invention include: providing a purge valve for an injection mold cooling system; providing such a valve which allows the operator to easily purge the cooling water from the mold and cooling lines; and providing such a valve which is compact, economical to manufacture, efficient in operation, capable of a long operating life and particularly well-adapted for the proposed usage thereof